Comparison Grandstream GWN7002 vs Grandstream GWN7001

The number of standard Gigabit Ethernet RJ-45 network connectors provided in the device design.

As the name suggests, these connectors provide data transfer rates up to 1 Gbps. Initially, Gigabit Ethernet was considered a professional standard, and even now the real needs for such speeds arise mainly when performing special tasks. Nevertheless, even relatively inexpensive computers are now equipped with gigabit network adapters, not to mention more advanced technology.

As for the number of connectors, it corresponds to the number of network devices that can be connected to the "switch" directly, without the use of additional equipment. At the same time, it is worth noting that in some "switches" individual connectors of this type are combined with optical SFP or SFP +. Such connectors are marked "combo" and are taken into account both when counting RJ-45 and when counting SFP / SFP +.

The number of optical network ports of the SFP standard provided in the design of the device. We emphasize that we are talking about "ordinary" SFPs; SFP+ data is usually listed separately.

Specifically, in switches, the marking “SFP” usually means a connector for fiber with a connection speed of 1 Gbps. Technically, this is not much compared to RJ-45 speeds; however, this connection format has a number of advantages. One of the main ones is a greater effective range: the mentioned gigabit standard works with a cable length of up to 550 m, and by the standards of optical fiber, this is still very little. True, the cable itself is sensitive to kinks and requires quite delicate handling; on the other hand, it is completely immune to electromagnetic interference. On the other hand, in general, the SFP format is noticeably less popular in network equipment than RJ-45; therefore, there are few ports of this type even in advanced devices ( 1 port or 2 ports, less often more). It is also worth considering that there may be so-called combo connectors that combine SFP and RJ-45; the presence of such ports is specified in the notes, they are taken into account both in the calculation of RJ-45 and in the calculation of SFP.

The standard for the PoE input provided in the device.

By itself, PoE (Power over Ethernet) technology makes it possible to transfer not only data over an Ethernet network cable, but also energy to power network devices. And the presence of a PoE input allows the router itself to receive power in a similar way. Note that there are special devices - the so-called PoE injectors - that allow you to add power to a regular network signal (that is, add PoE support to equipment that does not initially have such a function).

As for the PoE standards, they determine both the power supply and the main possibilities for coordinating the power source with the consumer - both must support the same standard, otherwise normal operation will be impossible. At the same time, formats that are marked like “802.3*” are called active; their common feature is that when a load is connected, the power source first “interrogates” it, checking whether the powered device complies with the requirements of the corresponding standard, and if so, what kind of power should be supplied to it. There is no such feature in the passive standard. And here is a more detailed description of specific options:

— 802.3at. A standard originally released back in 2009 and known as PoE +, or PoE type 2. The standard power received at this input is 25.5 W, with a voltage of 42.5 to 57 V and a pair power of up to 600 mA.

— 802.3af/at. This mar...king means that the PoE input supports both the 802.3at standard described above and the earlier 802.3af (PoE type 1). The second format is noticeably more modest in terms of capabilities: it provides power at the power input up to 13 W, input voltage 37 - 57 V and power in a pair of power wires up to 350 mA. Despite their "venerable age", many devices with 802.3af outputs are still in use today; so for the power input of the router, compatibility with this standard may not be superfluous. We only note that 802.3af covers as many as four so-called power classes (from 0 to 3), which differ in the specific number of watts at the output and input. So when connecting power from a device with this PoE standard, it does not hurt to further clarify compatibility by power class.

— Passive. The most simple and inexpensive standard, designed to be used mainly in entry-level equipment (since the implementation of active PoE standards is generally expensive). As mentioned above, the key difference from the formats described above is that the power supply supplies energy "as is" - with a strictly fixed voltage and power, without checking the characteristics of the load and without adjusting to it. This is what ensures low price and availability. On the other hand, when using a passive PoE input, care must be taken to ensure that the voltage and power of the power supply match the characteristics of the router; and such coordination can be quite difficult in light of the fact that the passive standard does not have strictly defined standards even for voltage, not to mention power. At the same time, the inconsistency leads to the fact that in the best case (if the output voltage / power is lower than tech required for the load), the power simply will not work, and in the worst case (with excess voltage / power), there is a high probability of overloads, overheating, and even breakdowns with fires - moreover such troubles may not occur immediately, but after a fairly considerable time. So you should pay attention to this option first of all in cases where simplicity and accessibility are more important than advanced power supply standards. At the same time, we note that some switches, which, in addition to the passive input, also have a passive PoE output, allow “cascade” connection - in the form of a serial chain of several devices powered by one external source (the main thing is that this source has enough power).

Separately, we emphasize that you should not try to connect an active power source to a passive input, and even more so vice versa. In the first case, the device simply will not pass the test that is carried out before power is applied, and the power will not turn on. And in the second case, serious failures and even accidents are possible: a passive power source supplies energy immediately, without checking the characteristics of the powered device, which creates the risk of overloads if the operating parameters do not match.

The PoE output(s) standard used by the router.

By itself, PoE (Power over Ethernet) technology allows you to transfer not only data over an Ethernet network cable, but also energy to power network devices. And the presence of a PoE output (outputs) makes it possible to power such devices from the network connectors of the device. This eliminates the need to lay additional wires or use independent power sources, which is especially important for some equipment, such as external IP surveillance cameras. And when using the so-called splitters - devices that divide the PoE cable signal into purely network data and power power - using such outputs, you can also power equipment that does not initially support PoE (the main thing is that their power characteristics correspond to the capabilities of the switch).

As for PoE standards, they determine not just the overall power supply, but also compatibility with specific devices: the consumer must support the same standard as the router, otherwise normal operation will be impossible. Nowadays, including in the connectors of "switches", you can find two types of such standards - active (802.3af, 802.3at, 802.3bt) and passive (one, that's what it's called). The main difference between these varieties is that active PoE provides for matching the power source and load in terms of voltage and power, while passive PoE does not have such functions, and energy is supplied “as is”, witho...ut adjustments. And here is a more detailed description of specific standards:

— 802.3af. The oldest active PoE power format in use today. It provides power at the power output up to 15 W (at the input of the consumer - up to 13 W), output voltage 44 - 57 V (at the input - 37 - 57 V) and power in a pair of supply wires up to 350 mA. Despite the "venerable age", it still continues to be widely used; so there are still quite a lot of routers that work only with 802.3af on sale (as of the end of 2021). However, it is worth considering that this standard immediately covers 4 so-called power classes (from 0 to 3), which differ in the maximum number of watts at the output and input. So when using 802.3af, it doesn't hurt to make sure that the output power will be sufficient for the selected load.

— 802.3af/at. A combination of two standards at once - the 802.3af described above and the newer 802.3at. The latter allows you to supply power up to 30 W (up to 25.5 W at the input of the powered device), uses a voltage of 50 - 57 V (42.5 - 57 V at the input), while the power in a pair of wires does not exceed 600 mA. Such a combination is relatively inexpensive, while it makes it possible to power a wide variety of external devices; so at the end of 2021, it is this type of PoE outputs that is most popular in routers.

— 802.3af/at, bt. Combination of 802.3af/at above with 802.3bt (PoE++, PoE type 3 or type 4). 802.3bt is the newest PoE power format; unlike earlier ones, it uses not 2, but 4 power wires, which allows you to supply very solid power to external devices - up to 71 V (at 90 W at the power output). Such capabilities are indispensable when supplying power to equipment with increased consumption - for example, external surveillance cameras, supplemented by heating systems. On the other hand, support for the 802.3bt standard significantly affects the cost of the device, and such a connection puts forward special requirements for the quality of cables. In addition, you need to keep in mind that this standard also includes the UPoE format created by Cisco and used in its equipment; and this standard (it is known as PoE type 3) has a more modest power - up to 60 W at the output (up to 51 W at the consumer's input). Yes, and the general standard 802.3bt includes two power classes - class 8, at which maximum performance is achieved, and class 7, where 75 watts are supplied to the output, and about 62 watts reach the consumer. So if you plan to use 802.3bt equipment, when choosing a router from this category, you must make sure that the power supply is enough for the connected devices to work properly.

— Passive. As already mentioned, the key difference between passive PoE and the active standards described above is that in this case the power output produces a strictly fixed power, without any automatic adjustments and adjustments for a specific device. The main advantage of this standard is its low cost: its implementation is much cheaper than active PoE, so such ports can be found even in entry-level routers. On the other hand, the aforementioned lack of auto-tuning makes it much more difficult to coordinate the equipment with each other - especially in light of the fact that different devices can differ markedly in the output / consumption of voltage and power (power). Because of this, when using passive PoE, you need to pay special attention to the compatibility of the source and load in these parameters. If there is no match, then in the best case (if the output voltage / power is lower than required), the power simply will not work, and in the worst case (with excess voltage / power), there is a high probability of overloads, overheating, and even breakdowns with fires - and such troubles may not occur immediately, but after a fairly long time. And it is definitely impossible to connect devices with active inputs to passive PoE outputs - for the same reasons.

In conclusion, it should be said that if the router has both an input with PoE support and several outputs with this function, then all the possibilities of such outputs, as a rule, can only be realized when the switch itself is powered from the outlet, and not from the PoE input. See "PoE Outputs" for details.

The number of PoE-enabled outputs (see above) provided in the design of the router.

In theory, this number corresponds to the maximum number of network devices that can be powered via PoE. However, in practice, two more points should be taken into account. The first and foremost is the total power delivered by such ports; most often it is indicated in the item "Total PoE power", and for models with one output - in the item "Power per PoE output". In any case, if the power consumption of the connected equipment is higher than this value, at best, the power from the switch simply “does not start”, and at worst, overloads and equipment breakdowns are possible.

The second nuance concerns routers, which themselves can be powered using Power over Ethernet. Recall that the power of such a power supply is very limited, so when it is used, most of the power usually goes to the operation of the switch itself, and there is little (if any) left to supply the PoE outputs. So when a device is powered via PoE, its own PoE outputs, at best, greatly “sag” in terms of capabilities (maximum power decreases, the number of simultaneously powered devices decreases), and at worst, they completely turn into ordinary network ports, without additional power. So if you plan to fully use the PoE outputs, you should take care to connect the switch itself to the network; this is especially true for models where there is more than one such output.

The total power that the router is capable of delivering to all PoE outputs.

See above for details on such exits; here we only recall that the general idea of PoE is to supply power over the same Ethernet cable that transmits data. The total power is given for models in which there is more than one such connector; it allows you to estimate the total power consumption of all PoE devices that can be connected to the router at the same time.

There are two important things to keep in mind when choosing a specific value. First, when multiple ports operate, the energy is usually shared equally among them; at the same time, the total power of the router does not always correspond to the sum of the maximum powers of all PoE outputs. For example, a model with 8 x 30W ports may not have a total of 240W (8*30W), but only 100W. In practice, this discrepancy means that with the simultaneous use of all connectors, each of them will be able to deliver not 30 W, but a maximum of 100/8 = 12.5 W. The second point is that the total power consumption of the load should ideally be no higher than 75% of the declared total PoE power - this provides an additional guarantee in case of malfunctions.

Separately, we note that if the router itself has a PoE input, then when using such power, the total power of the PoE outputs is noticeably reduced at best, and at worst, such outputs even turn into ordinary Ethernet ports. So in such models, data on the total PoE power is rel...evant only if the switch is powered by a regular outlet.